package cn.lili.modules.kit.core.kit;

import cn.hutool.core.codec.Base64;

import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.GeneralSecurityException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;

/**
 * 工具类 AesUtil
 *
 * @author 微信
 */
public class AesUtil {

  static final int KEY_LENGTH_BYTE = 32;
  static final int TAG_LENGTH_BIT = 128;
  private final byte[] aesKey;

  /** @param key APIv3 密钥 */
  public AesUtil(byte[] key) {
    if (key.length != KEY_LENGTH_BYTE) {
      throw new IllegalArgumentException("无效的ApiV3Key，长度必须为32个字节");
    }
    this.aesKey = key;
  }

  /**
   * 证书和回调报文解密
   *
   * @param associatedData associated_data
   * @param nonce nonce
   * @param cipherText ciphertext
   * @return {String} 平台证书明文
   * @throws GeneralSecurityException 异常
   */
  public String decryptToString(byte[] associatedData, byte[] nonce, String cipherText)
      throws GeneralSecurityException {
    try {
      Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

      SecretKeySpec key = new SecretKeySpec(aesKey, "AES");
      GCMParameterSpec spec = new GCMParameterSpec(TAG_LENGTH_BIT, nonce);

      cipher.init(Cipher.DECRYPT_MODE, key, spec);
      cipher.updateAAD(associatedData);

      return new String(cipher.doFinal(Base64.decode(cipherText)), StandardCharsets.UTF_8);
    } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
      throw new IllegalStateException(e);
    } catch (InvalidKeyException | InvalidAlgorithmParameterException e) {
      throw new IllegalArgumentException(e);
    }
  }
}
